DE112016005294T5 - Fuel distribution pipe - Google Patents

Abstract

Provided is a fuel rail which is connected to a fuel pipe and distributes and supplies fuel to a plurality of fuel injectors, the fuel rail comprising: a tubular base material forming a body of the fuel rail and a coating layer formed on a surface of the base material wherein the base material includes a sealing surface formed on an inner circumferential surface thereof and comes into pressure contact with the fuel pipe and wherein a thickness of the coating layer on the sealing surface is thinner than that of the coating layer on an outer peripheral surface of the fuel distribution pipe.

Description

Technical area

The present invention relates to a fuel distribution pipe in which fuel is distributed and supplied to a plurality of fuel injection devices.

State of the art

In a direct injection engine or the like, high pressure fuel compressed by a high pressure pump is distributed and supplied to a plurality of fuel injectors using a fuel distribution feeder. In the fuel distribution feeder, a fuel pump connected to the high-pressure pump is separably connected to a fuel distribution pipe that distributes and supplies fuel to the plurality of fuel injectors. Then, a front end portion of the fuel pipe on the side of the fuel distribution pipe is provided with a connection head portion, and a front end portion of the fuel distribution pipe on the side of the fuel pipe is provided with a sealing surface coming into pressure contact with the connection head portion.

Generally, fuel distribution tubes are formed of stainless steel such as SUS (Steel Use Stainless), however, carbon steel (iron) may be considered as a material to reduce costs and improve strength. However, when carbon steel is used as a material, there is a need to cover the surface with a coating as a corrosion resistance measure. In particular, an electrochemical or electroless nickel plating or an electroless nickel plating is formed on the surface of the fuel distribution tube and a zinc coating or a zinc coating or a zinc-nickel coating or a zinc coating is formed. Nickel coating formed on this. The electroless nickel plating is a coating for ensuring a corrosion resistance of an inner surface against fuel such as alcohol fuel and deteriorated fuel, and is formed on the entire surface of the fuel distribution pipe. The zinc coating or the zinc-nickel coating or the zinc-nickel coating is a coating or coating which is mainly used to ensure corrosion resistance to salt damage from the external environment, and is formed on the outer peripheral surface, both end surfaces and the sealing surface of the fuel distribution pipe.

quote list

patent literature

Patent Literature 1: Unexamined Japanese Patent Publication No. 2004-003455

Summary of the invention

Technical problem

Meanwhile, in the fuel distribution feeder, at the time of inspecting a vehicle, the fuel pipe is disconnected from the fuel distribution pipe in some cases. In such a case, after the inspection, the fuel pipe is reconnected to the fuel distribution pipe, but at this time there is a possibility that the coating formed on the sealing surface of the fuel distribution pipe may break and come off , If dissolved coating or plating penetrates into the fuel injector or the engine so that soiling occurs, there is a possibility that engine malfunction may occur.

In this regard, Patent Literature 1 describes a high-pressure fuel supply device which does not form a coating on the sealing surface. However, in the high-pressure fuel supply apparatus described in Patent Literature 1, since no coating is formed on the sealing surface, corrosion resistance of the sealing surface against alcohol fuel and deteriorated fuel can not be ensured.

Here, it is an object of one aspect of the present invention to provide a fuel distribution pipe capable of suppressing contamination due to a coating while ensuring a corrosion resistance of a sealing surface.

the solution of the problem

A fuel rail according to one aspect of the present invention is a fuel rail connected to a fuel pipe and distributes and supplies fuel to a plurality of fuel injectors, the fuel rail including: a tubular base material forming a body of the fuel rail and a coating layer; which is formed on a surface of the base material, wherein the base material includes a sealing surface formed on an inner peripheral surface thereof and comes into pressure contact with the fuel pipe, and wherein a thickness of the coating layer on the sealing surface thinner than that of the coating layer on a outer peripheral surface of the fuel distribution pipe.

In the fuel distribution pipe according to one aspect of the present invention, since the coating layer is formed on the surface of the base material, corrosion resistance of the fuel distribution pipe can be ensured. Further, since the thickness of the coating layer on the sealing surface is thinner than the thickness of the coating layer on the outer peripheral surface, it is possible to suppress the cracking of the coating layer due to the reconnection of the fuel pipe. Accordingly, it is possible to suppress contamination caused by the coating piece.

In the fuel distribution pipe, the coating layer may be composed of a plurality of layers, and the number of layers of the coating layer on the sealing surface may be smaller than the number of layers of the coating layer on the outer peripheral surface. In the fuel distribution pipe, since the thickness of the coating layer on the sealing surface is thinner than the thickness of the coating layer on the outer peripheral surface, it is possible to suppress contamination caused by the coating piece.

In the fuel distribution pipe, the coating layer may be composed of a plurality of layers, and a thickness of a specific layer which is any one of the coating layers on the sealing surface may be thinner than that of the specific layer on the outer peripheral surface. In the fuel distribution pipe, since the thickness of the coating layer on the sealing surface is thinner than the thickness of the coating layer on the outer peripheral surface, it is possible to suppress contamination caused by the coating piece.

In this case, a thickness of the specific layer on the sealing surface may be greater than 0% and equal to or less than 80% of the thickness of the specific layer on the outer circumferential surface. In the fuel distribution pipe, since the thickness of the specific layer on the sealing surface is set to be greater than 0% and equal to or less than 80% of the thickness of the specific layer on the outer peripheral surface, it is possible to cause contamination caused by the coating piece to further suppress.

In the fuel distribution pipe, the sealing surface may be formed in a tapered shape that increases in diameter toward an end surface. In the fuel distribution pipe, since the sealing surface is formed in a tapered shape, the adhesion with respect to the connection head portion of the fuel pipe is improved. In this case, a part within a position in which the connection head portion is to be in a pressure contact state also contacts the fuel, even on the sealing surface. However, since the coating layer is formed on the sealing surface, the corrosion resistance at the portion can be ensured.

In the fuel distribution pipe, the base material may be carbon steel. In the fuel distribution pipe, since the base material is carbon steel, it is possible to reduce costs as compared with a case where the base material is stainless steel.

In the fuel rail, the coating layer may be at least one of the coatings, nickel coating, zinc coating, and zinc alloy coating. In the fuel distribution pipe, since the coating layer is at least one of the coatings, nickel coating, zinc coating and zinc alloy coating, corrosion resistance can be sufficiently ensured. For example, in the case of the electrochemical or electroless nickel plating is possible to ensure a corrosion resistance to fuel, such as alcohol fuel and deteriorated fuel in the fuel contact section. Then, in the case of the zinc plating or zinc alloy plating, it is possible to ensure corrosion resistance against salt damage from the outside environment.

Meanwhile, the present inventors further studied carefully about the peeling of the coating from the sealing surface, and found that the number and size of the coating pieces released from the sealing surface was small when the Vickers hardness of the base material was set equal to or higher than a given hardness. From such knowledge, in the fuel distribution pipe, the Vickers hardness [Hv] of the sealing area of the base material may be 230 or more. In the fuel distribution pipe, since the Vickers hardness of the sealing surface of the base material is equal to or more than 230, deformation of the sealing surface in the moored state is suppressed. Accordingly, the breakage of the coating layer on the sealing surface is suppressed, and the number and size of the coating pieces released from the sealing surface can be made small.

The fuel distribution pipe may further include a connection portion provided with the sealing surface and connected to the fuel pipe, a pipe portion fixed to the fuel distribution pipe, and a plurality of cup portions fixed to the pipe portion and the plurality of fuel injection devices, respectively attached are included. In the fuel distribution pipe, since the connecting portion and the plurality of cup portions are fixed to the pipe portion, the fuel sent from the fuel pipe can be appropriately distributed and supplied to the plurality of fuel injection devices.

Advantageous Effects of the Invention

According to one aspect of the present invention, it is possible to suppress a fouling caused by a coating piece while ensuring the corrosion resistance of a sealing surface.

list of figures

• 1 FIG. 10 is a plan view showing a part of a fuel distribution feeder. FIG.
• 2 FIG. 12 is a cross-sectional view showing a connection portion between a fuel distribution pipe and a fuel pipe. FIG.
• 3 FIG. 12 is a schematic cross-sectional view showing the fuel distribution pipe. FIG.
• 4 is a schematic cross-sectional view showing the fuel distribution pipe, wherein 4 (a) is a schematic cross-sectional view taken along a line IV (a) -IV (a), which in 3 can be seen, taken, and 4 (b) is a schematic cross-sectional view taken along a line IV (b) -IV (b), which in 3 can be seen, is taken.
• 5 Fig. 10 is a diagram illustrating a coating layer forming method.
• 6 FIG. 12 is a schematic cross-sectional view showing a modified example of the fuel distribution pipe. FIG.
• 7 is a schematic cross-sectional view showing the fuel distribution pipe, wherein 7 (a) is a schematic cross-sectional view taken along a line VII (a) -VII (a), which in 6 can be seen, taken, and 7 (b) is a schematic cross-sectional view taken along a line VII (b) -VII (b), which in 6 can be seen, is taken.
• 8th Fig. 10 is a diagram illustrating a coating layer forming method.
• 9 FIG. 12 is a schematic cross-sectional view showing a fuel distribution pipe of a comparative example. FIG.
• 10 Fig. 12 is a graph showing an average number of collected foreign substances of Examples 1 to 4 and Comparative Example.
• 11 Fig. 12 is a graph showing the average weight of collected foreign substances of Examples 1 to 4 and Comparative Example.
• 12 Fig. 10 is a diagram showing a Vickers hardness measurement position.
• 13 is a graph showing a Vickers hardness measurement result.

Description of the embodiments

Hereinafter, a fuel distribution pipe according to an embodiment will be described with reference to the drawings. In the drawings, the same or corresponding components are identified by the same reference numerals, and a repetitive description thereof will be omitted.

1 FIG. 10 is a plan view showing a part of a fuel distribution feeder. FIG. As it is in 1 is seen, a fuel distribution feeder 1 used to pressurize high-pressure fuel, which is compressed by a high-pressure pump (not shown), to a fuel injector 2 Provided to meet, disperse and deliver to every cylinder of an engine (not to be seen). The fuel distribution feeder 1 is also called a fuel distribution pipe, a common rail or a common rail or the like.

The fuel distribution feeder 1 contains a fuel distribution pipe 3 , the high pressure fuel to the plurality of fuel injectors 2 distributes and delivers, and a fuel pipe 4 , the high pressure fuel, which is compressed by the high pressure pump, to the fuel distribution pipe 3 supplies.

The fuel distribution pipe 3 contains a pipe section 31 and a plurality of cup sections 32 ,

The pipe section 31 stores fuel that is supplied from the high pressure pump under pressure to the fuel to the plurality of fuel injectors 2 to deliver. The pipe section 31 is formed in a circular pipe shape extending linearly along a cylinder-row direction (a crankshaft direction) of the engine. An inner peripheral surface of the pipe section 31 forms a fuel passage. In addition, the pipe shape of the pipe section must 31 does not have the circular tubular shape extending linearly, and may be of various shapes.

A lid section 33 , the one end section of the pipe section 31 is blocked, is at an end portion of the pipe section 31 attached and a connecting section 34 that with the fuel pipe 4 is connected to the other end portion of the pipe section 31 attached. The lid section 33 and the connecting portion 34 may be brazed to the pipe section, for example 31 be attached. One or the one end portion of the pipe section 31 indicates an end portion opposite to the fuel pipe 4 is, under both end portions of the pipe section 31 , The other end portion of the pipe section 31 indicates an end portion on the side of the fuel pipe 4 under both end portions of the pipe section 31 , In addition, a fuel pressure transmitter or the like may be provided with an end portion of the pipe section 31 instead of the lid section 33 be connected.

2 FIG. 12 is a cross-sectional view showing a connection portion between the fuel distribution pipe and the fuel pipe. FIG. As it is in 1 and 2 can be seen, is the connecting section 34 formed in a circular tube shape. An inner peripheral surface of the connecting portion 34 forms a fuel passage. The connecting section 34 contains a flange section 341 , a fastening section 342 and a screw section 343 ,

The flange section 341 is located at the center portion of the connection portion 34 in the tube axis direction and is formed in a flange shape to increase outward in the radial direction in a diameter. The attachment section 342 is located on the side of one end surface 34b of the connection section 34 with respect to the flange portion 341 and is on the pipe section 31 attached. One or the one end surface 34b indicates an end surface opposite to the fuel pipe 4 is, under the two end surfaces of the connecting portion 34 in the tube axis direction. The screw section 343 is located on the side of the other end face 34c of the connection section 34 with respect to the flange portion 341 and is with the fuel pipe 4 connected. The other endface 34c indicates an end surface on the side of the fuel pipe 4 under both end surfaces of the connecting portion 34 in the tube axis direction. An outer peripheral surface of the screw portion 343 is provided with a penetration screw to connect to the fuel pipe 4 to be connected. An inner peripheral surface of the screw portion 343 is with a sealing surface 344 provided with the the fuel pipe 4 comes into pressure contact. The sealing surface 344 is also called a seat.

The sealing surface 344 is in a tapered shape (funnel shape) that extends to the other end face 34c increased in diameter, formed and a cross section through the tube axis of the connecting portion 34 has a linear shape. An inclination angle of the sealing surface 344 with respect to the tube axis of the connection section 34 can be set to 60 °, for example.

The cup section 32 is at each of the plurality of fuel injectors 2 attached and supplies the fuel that is in the pipe section 31 stored to each fuel injector 2 , The cup section 32 is on the pipe section 31 attaches and holds the fuel injector 2 such that there is a gap with respect to the fuel injector 2 is airtight. The cup section 32 For example, by brazing on the pipe section 31 be attached.

3 is a cross-sectional view showing a part of the fuel pipe. As it is in 1 to 3 can be seen, contains the fuel pipe 4 a pipe section 41 , a connection head section 42 and a connecting nut 43 ,

The pipe section 41 is between the high pressure pump and the fuel rail 3 and sends the high-pressure fuel, which is compressed by the high-pressure pump, to the fuel distribution pipe 3 , An inner peripheral surface of the pipe section 41 forms a fuel passage.

The connection head section 42 is with the fuel distribution pipe 3 connected. The connection head section 42 is formed in a circular tube shape. An inner peripheral surface of the connection head portion 42 forms a fuel passage. The connection head section 42 is on the pipe section 41 attached. The connection head section 42 can on the pipe section 41 by, for example, inserting the connecting head portion 42 in the pipe section 41 and brazing the inner peripheral surface of the joint head portion 42 and the outer peripheral surface of the pipe section 41 be attached.

A front end portion of the connecting head portion 42 is with a pressure contact portion 47 in pressure contact with the sealing surface 344 comes, provided. An outer peripheral surface of the pressure contact portion 47 is in a spherical surface shape, which is a center point on the pipe axis of the joint header section 42 has formed.

The connecting nut 43 connects and secures the connecting head portion 42 of the fuel pipe 4 with or at the connecting portion 34 of the fuel distribution pipe 3 , The connecting nut 43 is formed in a nut shape and a hole into which the connecting head portion 42 is inserted on the inside of the connecting nut 43 formed in the radial direction. The connecting nut 43 contains a hooking section 431 and a screw section 432 ,

The hooking section 431 is located at an end portion on the side of one end surface 43a the connecting nut 43 , One or the one end face 43a of the connecting nut 43 indicates an end face opposite to the fuel distribution pipe 3 is, under both end surfaces of the connecting nut 43 , Then the hooking section hooks 431 the connection head section 42 that from the other end face 43b the connecting nut 43 is inserted into the connecting nut 43 from the side of one end surface 43a one. The other endface 43b the connecting nut 43 indicates an end surface on the side of the fuel distribution pipe 3 under both end surfaces of the connecting nut 43 ,

The screw section 432 is located at one end portion at the side of the other end surface 43b the connecting nut 43 , An inner peripheral surface of the screw portion 432 is provided with an inlet screw to enter into the screw section 343 of the connection section 34 to be screwed in.

Then, when the screw section 432 the connecting nut 43 to the screw section 343 of the connection section 34 is moored, the hooking section pulls 431 the connection head section 42 to the connection section 34 out. Accordingly, the pressure contact portion comes 47 of the connection head portion 42 in pressure contact with the sealing surface 344 and are the fuel distribution pipe 3 and the fuel pipe 4 connected and fastened together.

Next is the fuel distribution pipe 3 regarding 3 and 4 described in more detail.

4 (a) is a schematic cross-sectional view taken along a line IV (a) -IV (a), which in 3 can be seen, taken, and 4 (b) is a schematic cross-sectional view taken along a line IV (b) -IV (b), which in 3 can be seen, is taken. As it is in 3 and 4 As can be seen, the fuel distribution pipe 3 contains a base material 3A formed in a circular pipe shape around a body of the fuel distribution pipe 3 to form, and a coating layer 3B on a surface of the base material 3A is formed.

The base material 3A forms the pipe section 31 , the variety of mug sections 32 , the lid section 33 and the connecting section 34 that was described above. The material of the base material 3A is not particularly limited, but may be carbon steel, stainless steel or the like. Among these materials, carbon steel is preferred from the viewpoint of cost and strength.

The Vickers hardness [Hv] of the sealing surface 344 of the base material 3A is desirably equal to 230 or more and more desirably equal to 250 or more. Further, it is desirable or desired that the Vickers hardness [Hv] of the sealing surface 344 of the base material 3A equal to the Vickers hardness [Hv] of the connecting head section 42 of the fuel pipe 4 in pressure contact with the sealing surface 344 is, or is greater than this. Meanwhile, the Vickers Hardness [Hv] is the sealing area 344 of the base material 3A desirably 500 or less and more desirably 400 or less from the viewpoint of a sealing property. In addition, if the base material 3A is formed of a material, the Vickers hardness of a surface except for the sealing surface 344 the same or substantially the same as the sealing surface 344 ,

When a material such as carbon steel, which has a low corrosion resistance, for or as the base material 3A is used, the coating layer is encased 3B the entire surface of the base material 3A to ensure the corrosion resistance of the product. Then the thickness of the coating layer 3B on the sealing surface 344 thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a of the fuel distribution pipe 3 , That is, the sealing surface 344 with the coating layer 3B is provided, but the coating layer 3B on the sealing surface 344 thinner than that of the outer peripheral surface 3a. The outer peripheral surface 3a of the fuel distribution pipe 3 corresponds to the outer peripheral surfaces of the pipe section 31 and the connection section 34 that are exposed to the outside and exposed to salt damage from the outside environment (see 2 ).

In particular, the coating layer contains 3B a first cladding layer 3B1 and a second cladding layer 3B2.

The first coating layer 3B1 is a coating mainly used to ensure corrosion resistance to fuel such as alcohol fuel and deteriorated fuel. As the first cladding layer 3B1, for example, an electroless nickel plating or an electroless nickel plating, a nickel electric plating, or the like is used. The first coating layer 3B1 is on the base material 3A educated. The thickness t1 of the first coating layer 3B1 is, for example, 3 μm or more and 10 μm or less from the viewpoint of corrosion resistance against the fuel.

The second coating layer 3B2 is a coating mainly used to provide corrosion resistance against salt damage from the outside environment. As the second coating layer 3B2, for example, a zinc coating, a zinc-nickel coating, or the like is used. The second coating layer 3B2 is formed on the first coating layer 3B1. The thickness t2 of the second coating layer 3B2 is, for example, 5 μm or more and 15 μm or less from the viewpoint of corrosion resistance to salt damage from the outside environment.

Then, the first coating layer 3B1 is on the entire surface of the base material 3A educated. Meanwhile, the second coating layer 3B2 is on the outer peripheral surface 3a of the base material 3A is formed, but not on the inner peripheral surface 3b , the other endface 34c and the sealing surface 344 of the base material 3A educated. The inner peripheral surface 3b is an area that forms a fuel passage.

For this reason, in the outer peripheral surface 3a the coating layer 3B a two-layer structure in which the first cladding layer 3B1 and the second cladding layer 3B2 are laminated in this order. Meanwhile, in the inner peripheral surface 3b the other end face 34c and the sealing surface 344 the coating layer 3B a single layer structure containing only the first coating layer 3B1. Accordingly, the thickness T2 of the coating layer 3B on the sealing surface 344 thinner than the thickness T2 of the coating layer 3B on the outer peripheral surface 3a , In particular, the thickness T1 of the coating layer 3B on the outer peripheral surface 3a for example, 8 μm or more and 25 μm or less. Meanwhile, the thickness T2 of the coating layer 3B on the sealing surface 344 for example, 3 μm or more and 10 μm or less.

Here will be an example of a method of forming the coating layer 3B regarding 5 described.

5 Fig. 10 is a diagram illustrating a coating layer forming method. Here, a case will be described in which an electroless nickel plating is formed as the first plating layer 3B1 and a zinc plating or zinc-nickel plating is formed as the second plating layer 3B2.

If the coating layer 3B on the base material 3A is formed, an electrochemical or electroless nickel coating on the entire surface of the base material 3A educated. Accordingly, the first coating layer 3B1 becomes on the entire surface of the base material 3A educated. The electrochemical nickel coating may be formed by the known method.

Next, as it is in 5 you can see the other end face 34c and the sealing surface 344 of the base material 3A provided with the first coating layer 3B1 through the lid 5 covered. The lid 5 may be any link as long as the sealing surface 344 can be covered. Then a zinc coating or zinc-nickel coating on the base material 3A formed in this state. The zinc coating or zinc-nickel coating can be formed by the known method. After the zinc coating or zinc-nickel coating is formed, the lid becomes 5 from the base material 3A separated. Accordingly, the second coating layer 3B2 becomes unique on the outer peripheral surface 3a formed without the second coating layer 3B2 on the sealing surface 344 to build. In addition, since the other end face 34c also through the lid 5 is covered in the embodiment, the second coating layer 3B2 not on the other end surface 34c formed in a manner similar to the sealing surface 344 , However, because the other endface 34c is not a surface that directly contacts the engaging component such as the sealing surface, the second coating layer 3B2 similarly to the outer peripheral surface 3a be formed while not through the lid 5 is covered.

In this way, in the fuel distribution pipe 3 according to the embodiment, since the coating layer 3B on the surface of the base material 3A is formed, a corrosion resistance of the fuel distribution pipe 3 be guaranteed. Furthermore, it is because the thickness of the coating layer 3B on the sealing surface 344 thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a is, possible, the breaking of the coating layer 3B due to reconnection or reconnection of the fuel pipe 4 to suppress. Accordingly, it is possible to suppress contamination caused by the coating piece.

As the number of layers of the coating layer 3B in the sealing area 344 and the outer peripheral surface 3a is different, the thickness of the coating layer 3B on the sealing surface 344 slightly thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a be made. Accordingly, it is because the thickness of the coating layer 3B on the sealing surface 344 thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a is possible to suppress contamination caused by the coating piece.

Because the sealing surface 344 is formed in a tapered shape, the adhesion with respect to the connecting head portion 42 of the fuel pipe 4 improved. In this case, a portion contacts within a position where the connection head portion 42 in a pressure contact state, the fuel itself is in or on the sealing surface 344 , However, since the coating layer 3B on the sealing surface 344 is formed, a corrosion resistance can be ensured at the section.

If the base material 3A Carbon steel, costs can be reduced, compared with a case in which the base material 3A Stainless steel is.

When the first coating layer 3B1 is an electroless nickel plating, it is possible to ensure corrosion resistance to fuel such as alcohol fuel or deteriorated fuel in a portion provided with the first plating layer 3B1. Further, when the second coating layer 3B2 is a zinc coating or zinc alloy coating, it is possible to ensure corrosion resistance to salt damage from the external environment in a portion provided with the second coating layer 3B2.

When the Vickers hardness [Hv] of the sealing surface 344 of the base material 3A is equal to 230 or more, a deformation of the sealing surface becomes 344 suppressed during mooring. Accordingly, the break-up of the coating layer 3B on the sealing surface becomes 344 Suppresses and can reduce the number and size of the dissolved coating pieces from the sealing surface 344 be made small.

Because the connecting section 34 and the multitude of cup sections 32 to the pipe section 31 can be bound to the fuel coming from the fuel pipe 4 is sent, due to the variety of fuel injectors 2 distributed and delivered.

While preferred embodiments of the invention have been described above, the invention is not limited to the embodiments described above.

For example, when the coating layer is composed of a plurality of layers, similarly to the fuel distribution pipe 13 shown in FIG 6 and 7 It can be seen that the thickness of the specific layer corresponding to any layer of the coating layers on the sealing surface is thinner than the thickness of the specific layer on the outer peripheral surface. In this case, it is desirable that the specific layer is the outermost layer of the coating layer. Furthermore, it is desirable that the thickness of the specific layer on the sealing surface is greater than 0% and equal to or less than 80% of the thickness of the specific layer on the outer circumferential surface.

6 FIG. 12 is a schematic cross-sectional view showing a modified example of the fuel distribution pipe. FIG. 7 (a) is a schematic cross-sectional view taken along a line VII (a) -VII (a), which in 6 can be seen, taken, and 7 (b) is a schematic cross-sectional view taken along a line VII (b) -VII (b), which in 6 can be seen, is taken. In the fuel distribution pipe 13 , this in 6 and 7 As can be seen, the second coating layer 3B2 is also on the other end surface 34c and the sealing surface 344 of the base material 3A apart from the outer peripheral surface 3a of the base material 3A formed, unlike the first embodiment. However, the second coating layer 3B2 is on the sealing surface 344 thinner than the second coating layer 3B2 on the outer peripheral surface 3a , That is, the second coating layer 3B2, which is the outermost layer of the coating layer 3B is, the specific layer will be. In particular, the thickness t2 of the second cladding layer 3B2 is the outer peripheral surface 3a for example, 5 μm or more and 15 μm or less, in a similar manner to the embodiment described above. Meanwhile, the thickness t2 of the second coating layer 3B2 is on the sealing surface 344 for example 1 μm or more or 12 μm or less.

For this reason, in one of the surfaces, outer peripheral surface 3a and sealing surface 344 , the coating layer 3B a two-layer structure in which the first cladding layer 3B1 and the second cladding layer 3B2 are laminated in this order. However, since the thickness of the second coating layer 3B2 is on the sealing surface 344 is diluted, the thickness T2 of the coating layer 3B on the sealing surface 344 thinner than the thickness T2 of the coating layer 3B on the outer peripheral surface 3a , In particular, the thickness T1 of the coating layer 3B on the outer peripheral surface 3a for example, 8 μm or more and 25 μm or less. Meanwhile, the thickness T2 of the coating layer 3B on the sealing surface 344 for example, 4 μm or more and 22 μm or less.

Here will be an example of a method of forming the coating layer 3B , in the 6 and 7 can be seen with reference to 8th described.

8th Fig. 12 is a diagram illustrating the coating layer forming method. Here, a case will be described in which an electroless nickel plating is formed as the first plating layer 3B1 and a zinc plating or zinc-nickel plating is formed as the second plating layer 3B2.

If the coating layer 3B on the base material 3A is formed, an electrochemical or electroless nickel coating on the entire surface of the base material 3A formed, and in similar Way as in the embodiment described above. Accordingly, the first coating layer 3B1 becomes on the entire surface of the base material 3A educated.

Next, as it is in 8th You can see a zinc coating or zinc-nickel coating on the base material 3A formed while the auxiliary cathode 6 (the dummy electrode) near the sealing surface 344 is arranged. Then, the second coating layer 3B2 of the zinc plating or zinc-nickel plating on the outer peripheral surface becomes 3a , the other endface 34c and the sealing surface 344 of the base material 3A educated. However, because of the zinc coating or zinc-nickel coating on the auxiliary cathode 6 The zinc plating or zinc-nickel plating is not easy on the sealing surface 344 educated. As a result, that is on the sealing surface 344 diluted second coating layer 3B2 diluted. Accordingly, that is on the sealing surface 344 formed coating layer 3B thinner than those on the outer peripheral surface 3a formed coating layer 3B ,

In this way, since the thickness of the second coating layer 3B2 on the sealing surface 344 and the outer peripheral surface 3a is different, the thickness of the coating layer 3B on the sealing surface 344 slightly thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a be made. Accordingly, it is because the thickness of the coating layer 3B on the sealing surface 344 thinner than the thickness of the coating layer 3B on the outer peripheral surface 3a is possible to suppress contamination caused by the coating piece.

In this case, since the thickness of the second coating layer 3B2 is on the sealing surface 344 is set to be greater than 0% and equal to or less than 80% of the thickness of the second coating layer 3B2 on the outer peripheral surface 3a, it is possible to further suppress contamination caused by the coating piece.

Furthermore, in 6 and 7 a case has been described in which the second coating layer 3B2 corresponding to the outermost layer is the specific layer, however, the specific layer may be, for example, the first coating layer 3B1 as long as the specific layer is any one of the coating layers.

In the embodiment described above, a case has been described in which the coating layer 3B is composed of two or more layers, but the overcoat layer may be 3B be composed of one layer or three or more layers.

Examples

Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

example 1

First, a pipe section, a plurality of cup sections, and a connecting section as a base material were temporarily welded and put in an oven to be brazed. Next, an electrochemical nickel plating was formed on the entire surface of the base material. Next, a zinc-nickel plating was formed on the base material while arranging an auxiliary cathode in the vicinity of a sealing surface of the joint portion (see FIG 8th ). At this time, the zinc-nickel coating formed on the sealing surface was adjusted to have a layer thickness of 80% of the zinc-nickel coating formed on the outer peripheral surface. Accordingly, a fuel distribution pipe of Example 1 in which the zinc-nickel plating formed on the sealing surface was thinner than the zinc-nickel plating formed on the outer peripheral surface was obtained (see 6 ). Five fuel distribution pipes of Example 1 were prepared.

Example 2

A fuel distribution pipe of Example 2 was obtained by the same method as that of Example 1 except that a zinc-nickel plating formed on a sealing surface was adjusted to have a film thickness of 50% of a zinc-nickel film formed on an outer peripheral surface. To have cover (see 6 ). Five fuel distribution pipes of Example 2 were prepared.

Example 3

A fuel distribution pipe of Example 3 was obtained by the same method as that of Example 1 except that a zinc-nickel plating formed on a sealing surface was adjusted to have a film thickness of 30% from a zinc-nickel film formed on an outer peripheral surface. To have cover (see 6 ). Five fuel distribution pipes of Example 3 were prepared.

Example 4

First, a fuel pipe, a plurality of cup portions, and a connecting portion as a base material were temporarily welded and put in an oven to be brazed. Next, an electrochemical nickel plating was formed on the entire surface of the base material. Next, a sealing surface of the connecting portion was covered by a lid, a zinc-nickel coating was formed on the base material in this state, and the lid was separated from the base material (see FIG 5 ). Accordingly, a fuel distribution pipe of Example 4 in which a zinc-nickel coating was formed on an outer peripheral surface and a zinc-nickel coating was not formed on the sealing surface was obtained (see 3 ). Five fuel distribution pipes of Example 4 were prepared.

Comparative example

First, a pipe section, a plurality of cup sections, and a connecting section as a base material were temporarily welded and brazed in an oven. Next, an electrochemical nickel plating was formed on the entire surface of the base material. Next, a zinc-nickel coating was formed on the entire surface of the base material. Accordingly, a fuel distribution pipe of a comparative example in which the zinc-nickel plating formed on the sealing surface and the zinc-nickel plating formed on the outer peripheral surface had the same number of layers were prepared (see 9 ). Five fuel distribution pipes of a comparative example were prepared.

evaluation

For each of the fuel distribution pipes of Examples 1 to 4 and Comparative Example, the number and weight of coating pieces to be detached from and released from the sealing surface were measured after an engaging component was attached and detached. Specifically, a connecting nut was fastened to the fuel rail and the joint head portion was brought into pressure contact with the sealing surface. Next, the connection nut was disconnected so that the connection head portion was separated from the sealing surface. Then, for the fuel distribution pipes of Examples 1 to 4 and Comparative Example, foreign substances (coating pieces) existing therein were collected, and the average number and the average weight of collected foreign substances were measured. The average number of foreign substances collected is in 10 to see and the average weight of foreign substances collected is in 11 to see.

As it is in 10 As can be seen, in each of Examples 1 to 4, the average number and the average weight of foreign substances were smaller than those of the comparative example. Specifically, in Example 1, the average number of foreign substances was reduced by 30%, and the average weight of foreign substances was reduced by 70%, as compared with the comparative example. In Example 2, the average number of foreign substances was reduced by 40%, and the average weight of foreign substances was reduced by 90%, as compared with the comparative example. From such a result, it has been found that fouling of the coating can be reduced when the fuel pipe is refastened when the thickness of the coating layer on the sealing surface 344 is set at least 80% of the coating layer or less than that on the outer peripheral surface 3a to be.

Reference Example 1

First, three base materials of a fuel distribution pipe formed of S35C (mechanical construction carbon steel) were prepared. Then, the Vickers hardness of the sealing surface of each base material was measured. The measurement position was at eight positions a to h, as in 12 can be seen, stated. At the time of measuring the Vickers hardness, no coating layer was formed on the base material. The measurement result is shown in Table 1 and in 13 to see.

Next, an electrochemical nickel plating was formed on the entire surface of each base material. Next, a zinc-nickel coating was formed on the entire surface of each base material. Accordingly, three fuel distribution pipes of Reference Example 1 in which the zinc-nickel plating formed on the sealing surface and the zinc-nickel plating formed on the outer peripheral surface had the same film thickness were prepared (see 9 ). Table 1 Reference Example 1 (S35C) measuring position Vickers hardness [Hv] example 1 Example 2 Example 3 a 197 172 182 b 173 176 178 c 188 166 170 d 170 163 175 e 167 180 189 f 194 211 185 G 198 197 168 H 198 200 177

Reference Example 2

First, three base materials of a fuel distribution pipe formed of SCM435 (chromium-molybdenum steel) were prepared. Then, the Vickers hardness of the sealing surface was measured for each base material. The measurement position was at eight positions a to h, as in 12 can be seen, stated. At the time of measuring the Vickers hardness, no coating layer was formed on the base material. The measurement result is shown in Table 2 and in 13 to see.

Next, an electrochemical nickel plating was formed on the entire surface of each base material. Next, a zinc-nickel coating was formed on the entire surface of each base material. Accordingly, three fuel distribution pipes of Reference Example 2 in which the zinc-nickel plating formed on the sealing surface and the zinc-nickel plating formed on the outer peripheral surface have the same film thickness were prepared (see 9 ). Table 2 Reference Example 2 (SCM435) measuring position Vickers hardness [Hv] example 1 Example 2 Example 3 a 255 272 245 b 253 261 262 c 262 277 260 d 262 258 244 e 268 280 259 f 261 271 287 G 273 262 246 H 250 249 254

evaluation

For the fuel distribution pipes of Reference Examples 1 and 2, the number and maximum size of the coating pieces released from the sealing surface were measured. Specifically, a connecting nut was fastened to the fuel rail and the joint head portion was brought into pressure contact with the sealing surface. Next, the connection nut was disconnected so that the connection head portion was separated from the sealing surface. Then, for the fuel distribution pipes of Reference Examples 1 and 2, foreign substances (coating pieces) existing in them were collected, and the total number and maximum size of the collected foreign substances were measured. Table 3 shows the total number of foreign substances collected from the fuel distribution pipe of Reference Example 1, and Table 4 shows the total number of foreign substances collected from the fuel distribution pipe of Reference Example 2. Further, Table 5 shows the maximum size of foreign substances collected from the fuel distribution pipes of Reference Examples 1 and 2. Table 3 Reference Example 1 (S35C) Size of a foreign substance Total number of foreign substances 20 to 50 59 50 to 100 43 100 to 150 113 150 to 200 207 > 200 205 Table 4 Reference Example 2 (SCM435) Size of a foreign substance Total number of foreign substances 30 to 60 18 60 to 100 9 100 to 150 6 150 to 300 2 > 300 0 Table 5 Maximum size of a foreign substance Reference Example 1 (S35C) 838 μm Reference Example 2 (SCM435) 259 μm

As shown in Tables 1 and 2, and 13 The Vickers Hardness [Hv] of S35C was about 220 or less and the Vickers Hardness [Hv] of SCM435 was about 230 or more. Then, as shown in Tables 4 and 5, the total number of foreign substances and the maximum size of foreign substances of Reference Example 2 using SCM435 as a material were smaller than those of Reference Example 1 using S35C as a material. From such a result, it can be considered that the cracking of the coating layer on the sealing surface is suppressed, and the number and size of the coating pieces released from the sealing surface are made small, because the Vickers hardness [Hv] of the sealing surface is 230 or more in the embodiments and examples described above. This is because deformation of the sealing surface during mooring due to the hardness of the sealing surface equal to or greater than the joint head portion is suppressed when the average Vickers hardness [Hv] of the joint head portion press-contacted with the sealing surface comes, is about 230.

LIST OF REFERENCE NUMBERS

1: fuel distribution feeder, 2: fuel injection device, 3: fuel distribution pipe, 3A: base material, 3B: coating layer, 3B1: first coating layer, 3B2: second coating layer, 3a: outer peripheral surface, 3b: inner peripheral surface, 4: fuel pipe, 5: cover, 6: Auxiliary cathode, 13: fuel distribution pipe, 31: pipe section, 32: cup section, 33: cover section, 34: connecting section, 34b: one end surface, 34c: another end surface, 41: pipe section, 42: connecting head section, 43: connecting nut, 43a: one end surface, 43b : Other end surface, 47: pressure contact portion, 341: flange portion, 342: fixing portion, 343: screw portion, 344: sealing surface, 431: hooking portion, 432: screw portion.

Claims (9)

A fuel rail connected to a fuel pipe and distributing and delivering fuel to a plurality of fuel injectors, the fuel rail comprising: a tubular base material forming a body of the fuel distribution pipe, and a coating layer formed on a surface of the base material, wherein the base material includes a sealing surface formed on an inner circumferential surface thereof and comes into pressure contact with the fuel pipe, and wherein a thickness of the coating layer on the sealing surface is thinner than that of the coating layer on an outer circumferential surface of the fuel distribution pipe. Fuel distribution pipe according to Claim 1 wherein the coating layer is composed of a plurality of layers, and wherein the number of layers of the coating layer on the sealing surface is smaller than the number of layers of the coating layer on the outer peripheral surface. Fuel distribution pipe according to Claim 1 or 2 wherein the coating layer is composed of a plurality of layers, and wherein a thickness of a specific layer which is any layer of the coating layers on the sealing surface is thinner than that of the specific layer on the outer peripheral surface. Fuel distribution pipe according to Claim 3 wherein a thickness of the specific layer on the sealing surface is greater than 0% and equal to or less than 80% of the thickness of the specific layer on the outer circumferential surface. Fuel distribution pipe according to one of Claims 1 to 4 wherein the sealing surface is formed in a tapered shape that increases in diameter toward an end surface. Fuel distribution pipe according to one of Claims 1 to 5 , wherein the base material is carbon steel. Fuel distribution pipe according to one of Claims 1 to 6 wherein the coating layer is at least one of the coatings, nickel coating, zinc coating and zinc alloy coating. Fuel distribution pipe according to one of Claims 1 to 7 wherein a Vickers hardness [Hv] of the sealing area of the base material is 230 or more. Fuel distribution pipe according to one of Claims 1 to 8th , further comprising: a connection portion provided with the sealing surface and connected to the fuel pipe, a pipe portion fixed to the fuel distribution pipe, and a plurality of cup portions fixed to the pipe portion and respectively at the plurality are mounted by fuel injectors.

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